PR69301 don't assume atomic<T> can default construct T

	PR libstdc++/69301
	* include/std/atomic (atomic<T>::load, atomic<T>::exchange): Use
	aligned buffer instead of default-initialized variable.
	* testsuite/29_atomics/atomic/69301.cc: New test.
	* include/experimental/memory (observer_ptr::release): Use reserved
	name.
	* include/ext/pointer.h (_Pointer_adapter::operator++(int))
	(_Pointer_adapter::operator--(int)): Likewise.

From-SVN: r244588

libstdc++-v3/ChangeLog

 2017-01-18  Jonathan Wakely  <jwakely@redhat.com>
 
+	PR libstdc++/69301
+	* include/std/atomic (atomic<T>::load, atomic<T>::exchange): Use
+	aligned buffer instead of default-initialized variable.
+	* testsuite/29_atomics/atomic/69301.cc: New test.
+	* include/experimental/memory (observer_ptr::release): Use reserved
+	name.
+	* include/ext/pointer.h (_Pointer_adapter::operator++(int))
+	(_Pointer_adapter::operator--(int)): Likewise.
+
 	PR libstdc++/68925
 	* include/experimental/random (randint): Use temporary instead of
 	thread_local static.

libstdc++-v3/include/experimental/memory

@@ -124,9 +124,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       constexpr __pointer
       release() noexcept
       {
-	__pointer tmp = get();
+	__pointer __tmp = get();
 	reset();
-	return tmp;
+	return __tmp;
       }
 
       constexpr void

libstdc++-v3/include/ext/pointer.h

@@ -449,9 +449,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       inline _Pointer_adapter 
       operator++(int)
       {
-        _Pointer_adapter tmp(*this);
+        _Pointer_adapter __tmp(*this);
         _Storage_policy::set(_Storage_policy::get() + 1);
-        return tmp;
+        return __tmp;
       }
   
       inline _Pointer_adapter& 
@@ -464,9 +464,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       inline _Pointer_adapter
       operator--(int) 
       {
-        _Pointer_adapter tmp(*this);
+        _Pointer_adapter __tmp(*this);
         _Storage_policy::set(_Storage_policy::get() - 1);
-        return tmp;
+        return __tmp;
       }
   
     }; // class _Pointer_adapter

libstdc++-v3/include/std/atomic

@@ -245,36 +245,40 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       _Tp
       load(memory_order __m = memory_order_seq_cst) const noexcept
       {
-        _Tp tmp;
-	__atomic_load(std::__addressof(_M_i), std::__addressof(tmp), __m);
-	return tmp;
+	alignas(_Tp) unsigned char __buf[sizeof(_Tp)];
+	_Tp* __ptr = reinterpret_cast<_Tp*>(__buf);
+	__atomic_load(std::__addressof(_M_i), __ptr, __m);
+	return *__ptr;
       }
 
       _Tp
       load(memory_order __m = memory_order_seq_cst) const volatile noexcept
       {
-        _Tp tmp;
-	__atomic_load(std::__addressof(_M_i), std::__addressof(tmp), __m);
-	return tmp;
+        alignas(_Tp) unsigned char __buf[sizeof(_Tp)];
+	_Tp* __ptr = reinterpret_cast<_Tp*>(__buf);
+	__atomic_load(std::__addressof(_M_i), __ptr, __m);
+	return *__ptr;
       }
 
       _Tp
       exchange(_Tp __i, memory_order __m = memory_order_seq_cst) noexcept
       {
-        _Tp tmp;
+        alignas(_Tp) unsigned char __buf[sizeof(_Tp)];
+	_Tp* __ptr = reinterpret_cast<_Tp*>(__buf);
 	__atomic_exchange(std::__addressof(_M_i), std::__addressof(__i),
-			  std::__addressof(tmp), __m);
-	return tmp;
+			  __ptr, __m);
+	return *__ptr;
       }
 
       _Tp
       exchange(_Tp __i,
 	       memory_order __m = memory_order_seq_cst) volatile noexcept
       {
-        _Tp tmp;
+        alignas(_Tp) unsigned char __buf[sizeof(_Tp)];
+	_Tp* __ptr = reinterpret_cast<_Tp*>(__buf);
 	__atomic_exchange(std::__addressof(_M_i), std::__addressof(__i),
-			  std::__addressof(tmp), __m);
-	return tmp;
+			  __ptr, __m);
+	return *__ptr;
       }
 
       bool

libstdc++-v3/testsuite/29_atomics/atomic/69301.cc

+// Copyright (C) 2017 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-do run { target c++11 } }
+
+#include <atomic>
+#include <testsuite_hooks.h>
+
+struct NonDefaultConstructible
+{
+  NonDefaultConstructible(int i) : val(i) { }
+  int val;
+};
+
+template class std::atomic<NonDefaultConstructible>;
+
+void
+test01()
+{
+  std::atomic<NonDefaultConstructible> a(1);
+  const auto n1 = a.exchange(2);
+  VERIFY( n1.val == 1 );
+  const auto n2 = a.load();
+  VERIFY( n2.val == 2 );
+}
+
+void
+test02()
+{
+  volatile std::atomic<NonDefaultConstructible> a(1);
+  const auto n1 = a.exchange(2);
+  VERIFY( n1.val == 1 );
+  const auto n2 = a.load();
+  VERIFY( n2.val == 2 );
+}
+
+int
+main()
+{
+  test01();
+  test02();
+}